Hybrid-electric and pure electric vehicles rely on a traction battery to provide power for propulsion. The traction battery typically includes a number of battery cells connected in various configurations. To ensure optimal operation of the vehicle, various properties of the traction battery may be monitored. One useful property is the battery state of charge (SOC) which indicates the amount of charge stored in the battery. The state of charge may be calculated for the traction battery as a whole and for each of the cells. The state of charge of the traction battery provides a useful indication of the charge remaining. The state of charge for each individual cell provides information that is useful for balancing the state of charge between the cells. Balancing of the cells is useful as differences in the state of charge between cells may cause some cells to be overcharged or undercharged relative to the other cells.